Hamilton, Ontario—As much as pharmacists seek to avoid them, adverse drug events can sometimes provide important information.

In one example, bleeding episodes in patients taking anticoagulants could be an indicator of higher cancer risk, according to a study presented at the recent European Society of Cardiology Congress in Munich, Germany. Researchers looked at participants in the Cardiovascular Outcomes for People Using Anticoagulation Strategies (COMPASS) trial.

“In patients with stable coronary artery disease or peripheral artery disease, the occurrence of major gastrointestinal bleeding predicts a substantial increase in new gastrointestinal cancer diagnoses, while major genitourinary bleeding predicts a substantial increase in new genitourinary tract cancer diagnoses,” explained John Eikelboom, MD, principal investigator of the COMPASS trial.

The COMPASS study team reported in the New England Journal of Medicine last year that in patients with coronary artery disease or peripheral artery disease, the combination of 2.5 mg twice daily of rivaroxaban, a direct oral anticoagulant (DOAC), and aspirin better reduced cardiovascular events compared with aspirin alone. The downside, however, was that more major bleeding events occurred in the combined drug group.

The trial included 27,395 patients with chronic stable coronary or peripheral artery disease from 602 centers in 33 countries. Participants were randomly divided among three groups: rivaroxaban 2.5 mg twice daily plus aspirin 100 mg once daily; rivaroxaban 5 mg twice daily; or aspirin 100 mg once daily, over a mean follow-up of 23 months. Results were compared to those in the aspirin-alone group.

Major bleeding was increased with the combination compared with aspirin (3.1% vs. 1.9%, hazard ratio [HR] 1.70, 95% confidence interval [CI] 1.40-2.05, P <.0001). Incidences of intracranial (0.3% vs. 0.3%, HR 1.16, 95% CI 0.67-2.00, P = .60) or fatal bleeding (0.2% vs.0.1%, HR 1.49, 95% CI 0.67-3.33, P = .32) did not go up significantly, however.

The new analysis looked at the link between the bleeding detected and subsequent cancer diagnoses. In a shocking result, investigators revealed that major gastrointestinal bleeding was associated with a 20-fold increase in new diagnoses of gastrointestinal cancer (9.3% vs. 0.7%, HR 22.6, 95% CI 14.9-34.3, P <.0001) and a two-fold increase in nongastrointestinal cancer (4.6% vs. 3.1%, HR 2.55, 95% CI 1.47-4.42, P <.0001).

At the same time, major nongastrointestinal bleeding was associated with a five-fold increase in new nongastrointestinal cancers (9.4% vs. 3.0%, HR 5.49, 95% CI 3.95-7.62, P <.0001), but not with new gastrointestinal cancer (0.5% vs. 0.8%, HR 0.85, 95% CI 0.21-3.45, P = 0.82).

“More than one in ten patients with major bleeding were subsequently diagnosed with cancer, and more than 20% of new cancer diagnoses were in patients who experienced bleeding,” explained Eikelboom, who is with the Population Health Research Institute, at McMaster University in Hamilton, Canada. “By reducing major cardiovascular events and mortality, the combination of rivaroxaban and aspirin already produces a clear net benefit, and if bleeding unmasks cancer it could potentially lead to the added benefit of improved cancer outcomes.”

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